The biologic and chemical characteristics of lymphoid cell surface antigens are under investigation. A human B lymphocyte antigen system has been identified and the genetic control shown to be linked to genes controlling HL-A antigens. Mixed lymphocyte reactions can be inhibited by the antisera directed against B lymphocyte specific antigens. Results to date indicate that the lymphocyte Fc receptor is not structurally related to the B cell antigens. In addition specific B lymphocyte antigens not found in the normal population have been identified in two disease states, glutin sensitive enteropathy and dermatitis herpetaformis. Complete homology of the first 20 N terminal amino acids have been found in 2 HL-A antigens controlled by different genes. Preliminary results of studies designed to determine the molecular and chemical nature of the B lymphocyte antigens has shown these antigens to be different in size from the major histocompatibility antigens HL-A. Patients with acute myelocytic and acute lymphocytic leukemia were immunized with a long term tissue culture cell line, RAJI, with or without BCG adjuvant therapy. All parameters of immune response to leukemia associated antigens increase in patients receiving the RAJI-BCG immunization.